Graphene sheets have become not only an item of tremendous theoretical and experimental interest over past several years, but are being developed for commercial use. They tend to be materials having high surfaces area and very low bulk densities, and as such, can be awkward to handle. For example, their low bulk densities mean that even small amounts of graphene sheets can require substantial storage and packaging volumes. This can make the storage, packaging, and transportation of commercial scale amounts of graphene sheets unwieldy and costly. Since many graphene sheets are derived directly or indirectly from the exfoliation of graphite into individual sheets or layered structures having a thickness of a few sheets, attempts to increase the bulk density could cause graphite to be reformed from graphene sheets. The resulting materials could have significantly lower surface areas and/or be less easily dispersed into another material, such as a matrix, binder, etc. It would thus be desirable to obtain a method of increasing the bulk density of graphene sheets without significant restacking of the sheets and/or significantly affecting the surface area of the graphene sheets and/or their dispersability.